Colored synthetic fiber

ABSTRACT

The present invention relates to the field of polymers, in particular that of polyester fibers, and relates more specifically to a process for manufacturing a colored synthetic fiber, and to the uses thereof. More particularly, the present invention relates to a process for manufacturing a colored synthetic fiber from a semicrystalline thermoplastic polyester based on isosorbide, said fiber being colored by means of an aqueous solution of at least one disperse dye. The present invention also relates to a fiber colored by a disperse dye and also to the use thereof in the field of furnishings, textiles or sporting goods. The process according to the invention makes it possible to obtain colored synthetic fibers having improved quality and improved stability of the dyeing.

TECHNICAL FIELD

The present invention relates to the field of polymers, in particular to the field of polyester fibers, and relates more specifically to a process for manufacturing a colored synthetic fiber, and to the uses thereof.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

Over the years, plastic materials have become essential for mass production because their thermoplastic nature allows them especially to be transformed at high speed into all kinds of objects or articles. In this context, significant developments have been made concerning synthetic fibers.

Synthetic fibers are mostly derived from petroleum and are generally favored because of their low production cost and ease of manufacture. The main known synthetic fibers are for example polyester, polyamide, polyurethane, elastane or acrylic fibers.

In order to provide polyester fibers with improved properties and to reduce the proportion of petroleum compounds in said fibers, document FR1657031, in the name of the applicant, discloses synthetic fibers obtained from a semicrystalline thermoplastic polyester comprising isosorbide.

Document U.S. Pat. No. 6,063,495 discloses polyester fibers manufactured from polymers having isosorbide units, terephthalic acid units, and ethylene glycol units. The resulting fibers are especially suitable for commercial or industrial use in textiles.

In view of the diversity of applications of synthetic fibers, it is necessary to have the widest possible color palette.

However, it is known that dyeing synthetic polyester fibers is very difficult because these materials are highly crystalline, absorb little water and do not swell. As a result, the penetration and migration of the dyes within the fibers is very limited and the coloring obtained is generally not satisfactory.

Document WO 2018/222017 discloses polyester fibers and the methods for preparing same. The polyester fiber is formed from a polyester resin having a structure in which a dicarboxylic acid and a diol are polymerized. The polyester resin comprises especially 1 to 20 mol % of diol units derived from isosorbide and 2 to 5 mol % of diol units derived from ethylene glycol, and also comprises 1.3% by weight of an oligomer.

For the manufacture of the actual resin, it is disclosed that an additive can be added during the preparation. In order to limit yellowing, the added additive can be a compound derived from cobalt, such as cobalt acetate, or if necessary, an organic compound such as an anthraquinone, perinone, azo or methine compound. In the case of an organic compound, an amount of 1 to 50 ppm must necessarily be respected in order to sufficiently mask the yellowing without altering the physical properties.

The addition of these organic compounds as an additive during the synthesis of the polymer therefore only makes it possible to compensate for the yellowing of the polymer but does not really make it possible to color or dye the polyester, and as a result, the fiber that may result.

The use of a coloring compound during polyester synthesis has a number of disadvantages. Indeed, large amounts of compounds cannot be used at the risk of altering the physical properties of the polyester obtained, as disclosed in document WO2018/222017, but also of generating an undesirable coloring in the polymerization reactor, which is not desirable for the synthesis processes, whether batch or continuous, as this would require additional cleaning operations.

Thus, the use of so-called “coloring” compounds in the synthesis stage makes it possible at best to compensate for the yellowing of the polyester but does not ultimately make it possible to obtain a specific coloring or hue of said polyester, for the previously mentioned reasons.

Document U.S. Pat. No. 3,223,752 relates to polyolefins modified to improve dyeability and spinnability. Particularly, this document discloses improved fiber-forming polyolefin compositions, as well as polyolefin fibers and filaments with improved dye affinity, particularly for disperse dyes, without significantly altering their physical properties. The improvement is obtained by combining the polyolefins with up to 1% to 20% by weight of modified polyesters. A modified polyester according to this document refers to polyesters prepared from dicarboxylic acids and glycols, the modification being carried out using a mixture of acids or glycols.

In the field of synthetic fibers, there is still a need to provide fibers with diverse and varied, uniform and high-quality colors.

It is therefore to the applicant's credit that they have responded to this need by proposing a process for manufacturing a colored synthetic fiber, said process not having the disadvantages of the already known solutions.

SUMMARY OF THE INVENTION

A first object of the present invention relates to a process for manufacturing a colored synthetic fiber comprising the following steps of: 1) providing a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one aromatic dicarboxylic acid unit (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, and the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g.

2) preparing the synthetic fiber from said semicrystalline thermoplastic polyester, 3) dyeing said synthetic fiber with an aqueous solution of at least one disperse dye.

Another object of the invention relates to a synthetic fiber colored by a disperse dye, said synthetic fiber consisting substantially of semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), at least one aromatic dicarboxylic acid (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g.

Another object of the invention relates to the use of the colored synthetic fiber disclosed hereinbefore in the field of furnishings, textiles or sporting goods.

DETAILED DESCRIPTION OF THE INVENTION

The present invention thus relates to a process for manufacturing a colored synthetic fiber comprising the following steps of:

1) providing a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one aromatic dicarboxylic acid (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g. 2) preparing the synthetic fiber from said semicrystalline thermoplastic polyester, 3) dyeing said synthetic fiber with an aqueous solution of at least one disperse dye.

As mentioned previously, it is generally accepted that the coloring of synthetic polyester fibers is very difficult due to the crystalline nature of these materials. Thus, they only absorb very small amounts of water and do not swell. As a consequence, the penetration and migration of dyes into these fibers is very limited and is generally not satisfactory for obtaining a uniform and high-quality result.

Surprisingly, the process according to the invention, by using thermoplastic polyester based on isosorbide and an aqueous solution of at least one disperse dye, makes it possible to obtain colored synthetic fibers that have improved dyeing quality.

Without wishing to be bound by any theory, the presence of isosorbide in the polyester according to the invention improves the dye affinity of the synthetic fiber with respect to an isosorbide-free polyester-based synthetic fiber, while also maintaining equivalent wash fastness.

The term “fiber” as used in the present invention is synonymous with the terms filaments and yarns, and thus includes continuous or discontinuous mono or multi-filaments, non-twisted or interwoven multi-filaments, and base yarns. This term also refers only to a fiber of synthetic origin and therefore does not include natural fibers.

The first step of the process according to the invention consists in providing a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one terephthalic acid unit (C), wherein the (A)/[(A)+(B)] molar ratio is from 0.05 to 0.30.

“(A)/[(A)+(B)] molar ratio” is intended to mean the molar ratio of 1,4:3,6-dianhydrohexitol units (A)/sum of the 1,4:3,6-dianhydrohexitol units (A) and of the aliphatic diol units (B) other than the 1,4:3,6-dianhydrohexitol units (A).

According to one particular embodiment, the (A)/[(A)+(B)] molar ratio is from 0.10 to 0.28, and preferentially from 0.15 to 0.25.

The monomer or unit (A) is a 1,4:3,6-dianhydrohexitol and may be selected from isosorbide, isomannide, isoidide, or a mixture thereof. Isosorbide, isomannide and isoidide can be obtained, respectively, by dehydration of sorbitol, mannitol and iditol.

According to a preferred embodiment, the 1,4:3,6-dianhydrohexitol unit (A) is isosorbide. It is for example marketed by the applicant under the trade name POLYSORB®.

The aliphatic diol unit (B) may be a linear, branched or cyclic aliphatic diol. It may also be a saturated or unsaturated aliphatic diol.

According to one particular embodiment, the aliphatic diol is a linear diol selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol and/or 1,10-decanediol.

According to another particular embodiment, the aliphatic diol unit (B) is a saturated branched non-cyclic aliphatic diol. Examples of this include 2-methyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, propylene glycol and/or neopentyl glycol.

According to one embodiment, the semicrystalline thermoplastic polyester is free of non-cyclic aliphatic diol units or comprises a molar amount of non-cyclic aliphatic diol units, with respect to the total number of monomer units of the polyester, of less than 1%; preferably, the polyester is free of non-cyclic aliphatic diol units.

According to another particular embodiment, the aliphatic diol unit (B) is a cyclic aliphatic diol. Examples of this include 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, spiroglycol, tricyclo[5.2.1.0^(2,6)]decanedimethanol (TCDDM), 2,2,4,4-tetramethyl-1,3-cyclobutanediol, tetrahydrofuran-dimethanol (THFDM), furandimethanol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,2-cyclohexanediol, dioxane glycol (DOG), norbornane diols, adamantane diols, pentacyclopentadecane dimethanols or a mixture of these diols.

Preferably according to this particular embodiment, the aliphatic diol unit (B) is 1,4-cyclohexanedimethanol. The aliphatic diol unit (B) may be in the cis configuration, in the trans configuration or may be a mixture of diols in cis and trans configuration.

According to one particular embodiment, the aliphatic diol unit (B) is an unsaturated aliphatic diol such as for example cis-2-butene-1,4-diol.

The aromatic dicarboxylic acid unit (C) may be selected from the aromatic dicarboxylic acids known to a person skilled in the art. The aromatic dicarboxylic acid may be a derivative of naphthalates, terephthalates, furanoates, thiophene dicarboxylate, pyridine dicarboxylate or even isophthalates or mixtures thereof. Advantageously, the aromatic dicarboxylic acid is a derivative of terephthalates and preferably, the aromatic dicarboxylic acid is terephthalic acid.

The reduced viscosity in solution of said semicrystalline thermoplastic polyester is greater than 50 ml/g. This reduced viscosity in solution is measured using an Ubbelohde capillary viscometer at 35° C. in ortho-dichlorophenol after dissolving the polymer at 130° C. while stirring, the concentration of polymer introduced being 5 g/I.

According to one particular embodiment, the semicrystalline thermoplastic polyester has a reduced viscosity in solution of 50 ml/g to 120 ml/g, preferably of 60 ml/g to 100 ml/g.

A semicrystalline thermoplastic polyester particularly suitable for the process according to the invention comprises a molar amount of 1,4:3,6-dianhydrohexitol units (A) ranging from 2.5 to 14 mol %, a molar amount of aliphatic diol units (B) other than the 1,4:3,6-dianhydrohexitol units (A) ranging from 31 to 42.5 mol %, and a molar amount of terephthalic acid units (C) ranging from 45 to 55 mol %.

The amounts of different units in the polyester may be determined by 1H NMR or by chromatographic analysis of the mixture of monomers resulting from complete hydrolysis or methanolysis of the polyester, preferably by 1H NMR.

Those skilled in the art can readily find the analysis conditions for determining the amounts of each of the units of the polyester. For example, from an NMR spectrum of a poly(1,4-cyclohexanedimethylene-co-isosorbide terephthalate), the chemical shifts relating to the 1,4-cyclohexanedimethanol are between 0.9 and 2.4 ppm and 4.0 and 4.5 ppm, the chemical shifts relating to the terephthalate ring are between 7.8 and 8.4 ppm and the chemical shifts relating to the isosorbide are between 4.1 and 5.8 ppm. The integration of each signal makes it possible to determine the amount of each unit of the polyester.

The semicrystalline thermoplastic polyester used according to the invention has a melting temperature ranging from 200 to 295° C., for example from 220 to 285° C. In addition, the semicrystalline thermoplastic polyesters have a glass transition temperature ranging from 40 to 120° C., for example from 50 to 115° C.

The glass transition temperatures and melting points are measured by conventional methods, especially using differential scanning calorimetry (DSC) using a heating rate of 10° C./min.

According to this method, the sample is first heated under a nitrogen atmosphere in an open crucible from 10 to 320° C. (10° C.·min-1), cooled to 10° C. (10° C.·min-1), then heated again to 320° C. under the same conditions as the first step. The glass transition temperatures are then taken at the mid-point of the second heating. Any melting points are determined on the endothermic peak (peak onset) at the first heating.

Advantageously, when the semicrystalline thermoplastic polyester has a heat of fusion greater than 10 J/g, preferably greater than 20 J/g, the measurement of this heat of fusion consists of subjecting a sample of this polyester to a heat treatment at 170° C. for 16 hours then of evaluating the heat of fusion by DSC by heating the sample at 10° C./min.

The semicrystalline thermoplastic polyester provided according to the first step of the process may be provided in the form of pellets or granules.

According to one particular embodiment, the semicrystalline thermoplastic polyester is conditioned in granule form, said granules having a residual moisture content of less than 300 ppm, preferentially less than 200 ppm such as for example about 75 ppm. These polyesters are particularly well suited to the manufacture of synthetic fibers and make it possible to obtain fibers that have better dye affinity with disperse dyes and have good washing stability.

According to one particular embodiment, the first step of the process according to the invention comprises providing a mixture of semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one aromatic carboxylic acid (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g. According to this embodiment, the step of preparing the synthetic fiber is carried out from said mixture.

In order to prepare a suitable semicrystalline thermoplastic polyester according to the process of the invention, a skilled person may refer to application FR1657031, also in the name of the applicant, which discloses the preparation protocol in detail. The content of this application is incorporated into the present description by reference.

The second step of the process according to the invention consists of preparing the synthetic fiber from the semicrystalline thermoplastic polyester provided in the previous step.

The synthetic fiber can be obtained according to the methods known to a skilled person. For example, the synthetic fiber can be obtained via melt spinning or by solution processes (wet or dry).

According to one particular embodiment, the synthetic fibers are manufactured by the melt spinning method.

The manufacture of synthetic fibers by the melt spinning method involves first melting the polyester in an extruder. The molten material is then sent under pressure through a die consisting of a multitude of holes. At the outlet of the die, the filaments are air-cooled, drawn and wound. Generally, a sizing product is applied at the lower part of the spinning path

According to one particular embodiment, the synthetic fiber obtained according to the second step of the process of the invention can be woven or knitted before the dyeing step.

The third step of the process according to the invention consists of dyeing the synthetic fiber with an aqueous solution of at least one disperse dye.

In the sense of the present invention, the aqueous solution of disperse dye is also referred to as “dye bath”.

A disperse dye is a weakly polar dye with a relatively small size, of the order of ten microns. This dye, due to its lack of solubilizing groups, is practically insoluble in water which means that it must be applied as an aqueous dispersion containing mostly dye particles.

Before being placed in aqueous solution, this type of dye can generally be in paste or powder form.

The disperse dye according to the invention is selected from azo-type disperse dyes, anthraquinone-type disperse dyes, methine-type dyes, nitro-type dyes, naphthoquinone-type dyes, aminoketone-type dyes and mixtures thereof.

According to one particular embodiment, the disperse dye is an azo-type dye. The azo-type dye can especially be selected from the di-azo or mono-azo dyes derived from azobenzene such as for example references Dispersed blue 165, C.I. Disperse Orange 5, C.I. Disperse Red 19, or C.I. Disperse Blue 183.

According to one particular embodiment, the disperse dye is an anthraquinone-type dye. By way of example, the anthraquinone-type dye can be selected from carmine, alizarin, purpurin, indanthrene blue, anthraquinone yellow, or anthraquinone red.

According to one particular embodiment, the disperse dye is a mixture of azo-type dye as defined hereunder and anthraquinone-type dye as defined hereinbefore.

Typically, anthraquinone-type dyes make it possible to obtain more uniform dyeing because they have a smaller molecular size than azo-type dyes. Thus, anthraquinone dyes are preferred for light shades and azo dyes are preferred for obtaining dark shades.

According to one particular embodiment, the aqueous solution may comprise an amount from 0.01% to 15% of disperse dye, preferably from 1 to 10% and particularly from 3 to 5%. The percentage being expressed by weight of dye relative to the total weight of the solution.

According to another particular embodiment, the aqueous solution of disperse dye used for the dyeing step according to the invention may comprise from 0.1 g/I to 10 g/l of dispersing agent. The dispersing agent has good wettability properties thus facilitating the dispersion of the dye in water but above all makes it possible to maintain a stable dispersion during the dyeing process.

The dispersing agent may belong to two classes of compounds. The first relates to condensation products of aromatic compounds containing sulfonated groups and the second to lignin sulfonates.

According to the process of the invention, the dyeing step is carried out by soaking in the aqueous solution of disperse dye.

According to one particular embodiment, the aqueous solution of disperse dye used for the dyeing step has a high temperature, that is to say a temperature of 120° C. to 140° C., preferably a temperature of 130° C.

According to this particular embodiment, the aqueous solution of disperse dye used is acidic. “Acidic” is intended in the present invention to mean that said solution has a pH of 3.5 to 5.5, preferably a pH of 4 to 5.

Also according to this embodiment, the soaking can advantageously be carried out for 10 to 120 minutes, preferably for 20 to 90 minutes, more preferably for 30 to 60 minutes.

According to one particular embodiment, the step of dyeing the synthetic fiber is carried out according to the following sequence: holding at 60° C. for 10 min, increasing the temperature at a rate of 1.5° C./min up to 80° C. and then at a rate of 1° C./min up to 130° C., holding at 130° C. for 45 min, and finally, reducing the temperature at a rate of 2.5° C./min up to 60° C.

According to this embodiment, the selection of this time/temperature cycle enables optimal dyeing of the synthetic fiber by the disperse dye.

According to one particular embodiment, after the dyeing step, the process comprises a step of stripping the dyed synthetic fiber so as to remove the disperse dye not fixed to said fiber.

According to this particular embodiment, the stripping may be carried out by soaking the synthetic fiber for 15 to 20 minutes in a bath at a temperature ranging from 65° C. to 80° C., said bath comprising for example a mixture of sodium hydroxide and sodium hydrosulfite. The stripping may optionally be followed by a hot rinse and a cold rinse.

According to this embodiment, the colored synthetic fiber obtained according to the process of the invention is free of any polymer other than that provided according to the first step.

A second object of the invention relates to a synthetic fiber colored by a disperse dye, said synthetic fiber consisting substantially of a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), at least one aromatic dicarboxylic acid (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g.

The dyed synthetic fiber according to the invention is likely to be obtained according to the previously disclosed process.

The semicrystalline thermoplastic polyester and the disperse dye are as disclosed previously.

“Consisting substantially of” is intended in the present invention to mean that 98% by weight, preferably 99% by weight, and particularly 100% by weight, relative to the total weight of the synthetic fiber consists of said semicrystalline thermoplastic polyester.

Another object of the invention is a dyed synthetic fiber as defined previously for use in the field of textiles, furnishings or sporting goods.

According to one particular embodiment, the fibers may be used for the production of textiles and non-woven. The textiles can especially be obtained by weaving or knitting.

A non-woven is a manufactured product consisting of a web, a cloth, a lap, or a mat of directionally or randomly distributed fibers, the internal cohesion of which is provided by mechanical, physical or chemical methods or else by a combination of these methods. An example of internal cohesion may be adhesive bonding, and results in obtaining a non-woven cloth, said non-woven cloth possibly then being made into the form of a mat of fibers.

The fibers may be transformed into non-woven according to the techniques known to a skilled person, such as the dry route, the melt route, the wet route or flash spinning.

By way of example, the formation of the non-woven by dry route may especially be carried out by calendering or by an air laid process. With regard to the production by melt route, it can be carried out by extrusion (spinbonding technology or spunbonded fabric) or by extrusion blow-molding (melt-blown).

The invention will be understood more clearly by means of the examples and figures below, which are intended to be purely illustrative and do not in any way limit the scope of protection.

FIGURES

FIG. 1 Synthetic fibers colored with the light hue bath. From left to right: Synthetic fiber F (PET); Synthetic fiber D (PEI10T), Synthetic fiber A (PT15T); Synthetic fiber B (PTI10T), Synthetic fiber C (PTT).

FIG. 2 Synthetic fibers colored with the medium hue bath. From left to right: Synthetic fiber F (PET); Synthetic fiber D (PEI10T), Synthetic fiber A (PT15T); Synthetic fiber B (PTI10T), Synthetic fiber C (PTT).

FIG. 3 Synthetic fibers colored with the dark hue bath. From left to right: Synthetic fiber F (PET); Synthetic fiber D (PEI10T), Synthetic fiber A (PT15T); Synthetic fiber B (PTI10T), Synthetic fiber C (PTT).

FIG. 4 Comparison of the colorings obtained with dye baths 1 to 3 on fabrics knitted with synthetic fibers E and F. From left to right: fabrics knitted with synthetic fiber F and dyed with bath 1; fabrics knitted with a synthetic fiber E and dyed with bath 1; fabrics knitted with a synthetic fiber F and dyed with bath 2; fabrics knitted with a synthetic fiber E and dyed with bath 2; fabrics knitted with a synthetic fiber F and dyed with bath 3; fabrics knitted with a synthetic fiber E and dyed with bath 3.

EXAMPLES

Materials and Methods

A: Synthesis of the Polyesters

Different polyesters were prepared for the manufacture of the synthetic fibers.

Polymer A (PTIT): poly(trimethylene-co-isosorbide terephthalate).

Polymer A is a semicrystalline thermoplastic polyester according to the invention.

The synthesis of this polymer is carried out by melt route in 2 steps, via a transesterification and a polycondensation step. This synthesis takes place in a 60-l reactor equipped with a stirrer with torque measurement, a distillation column, a vacuum line and a nitrogen inlet.

First, the reactor is preheated to 100° C. before being loaded with the previously prepared reaction mixture.

The reaction mixture consists of:

-   -   18.7 kg of dimethyl terephthalate,     -   0.915 kg of isosorbide,     -   9.049 kg of 1,3-propanediol,     -   18.66 g of titanium butoxide, used as catalyst,     -   6.32 g of tetrahydroxyl ammonium, used as etherification         inhibitor,     -   9.5 g of Hostanox PEPQ, used as antioxidant,     -   9.5 g of Irganox 1010, used as antioxidant.

The reactor is then inerted by 4 vacuum/nitrogen cycles.

The reaction medium is then heated to 220° C. for 1:30 h and then to 245° C. until the end of the trans-esterification reaction. This first step is carried out under 1.5 bar of nitrogen.

When the target transformation rate is reached, a decompression ramp is applied in order to obtain the maximum vacuum in 1:40 h and the temperature is increased to 255° C. after 80 minutes of vacuum ramp.

When the target torque is reached, the polymer is poured into a water bath and then granulated.

The polymer thus obtained has a reduced viscosity in solution (IV) of 73.7 ml/g.

The polymer pellets then undergo a post-condensation treatment in solid state in a 50-l glass flask heated by an oil bath, stirred and under nitrogen flow.

For the crystallization step, the oil bath is heated to 150° C. The flask is stirred and the granules are under nitrogen flow (flow rate=10 l/min). Crystallization is stopped after about 8 hours.

The pellets are then cooled under nitrogen to 40° C. to detach if necessary any pellets attached to the walls of the flask. Then, the oil bath is reheated to 210° C. while stirring and under nitrogen flow (10 l/min) for the post-condensation step. These conditions are maintained for 15 h.

The final polymer, denoted polymer A, has a final reduced viscosity in final solution IV of 102 ml/g, a molar ratio of isosorbide to diols of 5.2 mol %, a glass transition temperature Tg of 58° C., and a melting temperature Tm of 222° C.

Polymer B (PTIT) and Polymer C (PTT).

Polymer B is a semicrystalline thermoplastic polyester according to the invention while polymer C serves as comparison and does not contain isosorbide. These two polymers are obtained according to a process similar to that of polymer A and have the final properties mentioned in Table 1 hereunder.

TABLE 1 Amount of isosorbide Final IV Polymer reference (mol %) (ml/g) Tg (° C.) Tm (° C.) Polymer A PTI₅T 5.2 102 59 221 Polymer B PTI₁₀T 7.8 106 57 216 Polymer C PTT 0 99 56 228

Polymer D (PEIT): polyethylene-co-isosorbide terephthalate) (PEIT).

The synthesis of polymer D is carried out by melt route in 2 steps, via an esterification and a polycondensation step. This synthesis takes place in a 100-l reactor equipped with a stirrer with torque measurement, a distillation column, a vacuum line and a nitrogen inlet.

The reactor is first preheated to 100° C. before being loaded with the following reagents:

-   -   29 kg of terephthalic acid,     -   3.67 kg of isosorbide,     -   11.44 kg of ethylene glycol,     -   11.59 g of germanium oxide, used as catalyst,     -   2.65 g of cobalt acetate,     -   17.65 g of Hostanox, used as antioxidant,     -   17.65 g of Irganox 1010, used as antioxidant,     -   4.33 g of tetraethylammonium hydroxide, used as anti-DEG.

The reactor is then inerted by 4 vacuum/nitrogen cycles.

For the esterification step, the reaction medium is heated to 250° C. under 2.5 bar. The esterification is continued until a transformation rate of about 80% is obtained.

The pressure is then reduced in 15 minutes to atmospheric pressure (1024 hPa) in order to add phosphoric acid via an addition jar (3.53 g of phosphoric acid dissolved in 50 g of ethylene glycol).

A vacuum ramp is then applied to reach 3 mbar in 25 minutes. The temperature of the reactor is increased to 265° C. The polycondensation is monitored by a torque measurement.

When the target torque is reached the polymer is poured into a water tray and then granulated.

The polymer obtained has a reduced viscosity in solution (IV) of 54 ml/g.

The polymer pellets then undergo a post-condensation treatment in solid state in a 50-l glass flask heated by an oil bath, stirred and under nitrogen flow.

For the crystallization step, the oil bath is heated to 150° C. The flask is stirred and the granules are under nitrogen flow (flow rate=10 l/min). Crystallization is stopped after about 8 hours. The pellets are then cooled under nitrogen to 40° C. to remove any pellets attached to the walls of the flask. Then, the oil bath is reheated to 220° C. while stirring and under nitrogen flow (10 l/min) for the post-condensation step. These conditions are maintained for 90 h.

The final polymer denoted polymer D has a final reduced viscosity in solution (IV) of 106 ml/g, a ratio of isosorbide to diols of 11.9 mol %, a Tg of 91° C. and a Tm of 225° C.

Polymer E: (cyclohexanedimethylene-co-isosorbide terephthalate) (PITg)

The synthesis of polymer E was carried out according to example 3a of application WO2016/189239 A1. The polymer has the following properties: a molar ratio of isosorbide to diols of 15.2 mol %, a reduced viscosity in solution (IV) of 85 ml/g, a Tg of 109° C. and a Tm of 263° C.

Polymer F (PET):

Polymer F serves as a comparison and does not contain isosorbide. It is a commercial poly(ethylene terephthalate) from Invista.

B: Preparation of the Synthetic Fibers

Synthetic fibers A, B, D and E according to the invention were prepared by melt spinning on a pilot line from polymers A (PTIT), B (PTIT), D (PEIT), and E (PITg), respectively.

Comparative synthetic fibers C and F were also prepared from the isosorbide-free polymers C (PTT) and F (PET), respectively.

The extrusion temperature is 260° C. for polymers A (PTIT), B (PTIT) and C (PTT), and 300° C. for polymers D (PEIT), E (PITg) and F (PET).

The die used comprises a head with 48 holes having a diameter of 25 μm each, the material flow rate is of 2 kg/h, the drawing speed is 1200 m/min.

At the outlet of the die, cooling is done by air jet at room temperature (about 23° C.) then a sizing is applied to the surface of the fibers.

The fiber bundle is then passed over four pairs of buckets heated to different temperatures (between 30° C. and 115° C.) in order to adjust the mechanical properties, and the assembly is then wound.

The synthetic fibers obtained with each of the polyesters A to F are then soaked in dye baths.

C: Preparation of the Dye Baths

The disperse dyes used are marketed by Huntsman and listed hereunder:

-   -   yellow: references Teratop GWL-01 (anthraquinone type) and         Terasil W6GS (azo type)     -   red: references Terasil 3BL-01 (azo type) and Terasil W4BS (azo         type)     -   blue: references Terasil 3RL-02 (anthraquinone type) and Terasil         WBLS (azo type).

For each dye bath, three dyes are mixed with water, a dispersing agent (Univadine DIF, 1 g/L) and an anti-creasing agent (Albafluid CD, 1 g/L).

The mixture has a pH of 5 controlled by adding acetic acid in order to obtain the dye bath for each disperse dye.

Three dye baths are thus prepared by varying the amount of dye in order to obtain light, medium and dark colors. The amounts of each dye used are set out in Table 2 hereunder.

TABLE 2 Bath no. Dye used Amount of dye Light hue 1 Yellow 0.21% Teratop GWL-01 Red 0.036% Terasil 3BL-01 Blue 0.034% Terasil 3RL-02 Medium hue 2 Yellow 0.53% Teratop GWL-01 Red 0.1% Terasil 3BL-01 Blue 0.1% Terasil 3RL-02 Dark hue 3 Yellow 0.6% Terasil W6GS Red 0.65% Terasil W4BS Blue 0.3% Terasil WBLS

D: Dyeing of the Synthetic Fibers

The polyester synthetic fibers were colored with the light, medium and dark hues. For each of the dye baths, all the different fibers were put in the same bottle for dyeing.

The bottles are placed on an Ahiba Nuance top speed bottle-turner marketed by Datacolor.

The dyeing is carried out according to the time/temperature cycle having the following successive steps:

-   -   inserting the fibers into the dyeing solution at room         temperature (about 23° C.) then heating the whole to 60° C.,     -   holding at 60° C. for 10 min, then,     -   increasing the temperature at a rate of 1.5° C./min up to 80°         C., then,     -   increasing the temperature at a rate of 1° C./min up to 130° C.,         then,     -   holding at 130° C. for 45 min, and finally,     -   reducing the temperature at a rate of 2.5° C./min to 60° C.

The various synthetic fibers are then recovered. Those dyed with baths 2 and 3 undergo an additional step of stripping in order to remove the excess disperse dye.

The stripping is carried out at 70° C. for 20 min in a bath comprising:

-   -   4 g/l of caustic soda, and     -   2 g/l of sodium hydrosulfite.

At the end of the 20 min, the synthetic fibers are hot and cold rinsed.

E: Test of Wash Fastness of the Dyes

Using the synthetic fibers E (PITg), three textiles are prepared and dyed with the light, medium and dark hue baths, respectively. The dyeing is carried out according to the previously disclosed protocol.

The same is done using the synthetic fibers F (PET).

For each of the textiles, the wash fastness is evaluated by means of a color fastness test carried out in accordance with standard ISO 105-006:2010.

The test comprises a step of washing the textiles at 40° C. for 30 min in 150 ml of detergent followed by a step of rinsing in two baths of water at 40° C.

Each textile is washed with a white strip of fabric made of 6 different materials, namely wool, acrylic, polyester, polyamide, cotton and acetate. This white strip of fabric serves as a control and thus makes it possible to check, where appropriate, whether the dye has bled out of the textile and to know onto what type(s) of material it has bled.

Results

The colored synthetic fibers obtained with the different baths are presented in FIGS. 1 to 3 .

For the 3 hues tested, the synthetic fibers A, B, D, E obtained with the semicrystalline thermoplastic polyesters according to the invention absorb very rapidly a very large part of the dye. The coloring obtained is perfectly uniform and has a high-quality visual appearance.

Moreover, the dyeing kinetics are much faster with the synthetic fibers according to the invention than for comparative isosorbide-free synthetic fibers C and F in PTT and PET, respectively.

In order to confirm these results, color measurements were taken using a Konica Minolta spectrocolorimeter. The samples are placed on the cell and the measurement is taken in reflection mode.

The delta L corresponds to the difference in lightness (light or dark). The delta a corresponds to the difference in greenness-redness and finally, the delta b corresponds to the difference in blueness-yellowness.

The results of the color measurements are presented in Table 3 hereunder:

TABLE 3 Synthetic fiber Delta L Delta a Delta b Dark hue F (PET) D (PEI10T) −20.1 1.3 −4.75 C (PTT) A (PTI5T) −1.6 0.3 −0.85 B (PTI10T) −1.6 0.7 −1.25 Medium hue F (PET) D (PEI10T) −25.1 6.7 3.4 C (PTT) A (PTI5T) 0.6 1.65 1.2 B (PTI10T) −0.9 1 0.3 Light hue F (PET) D (PEI10T) −25.2 32 5.6 C (PTT) A (PTI5T) −0.6 1.3 1.5 B (PTI10T) 0.5 1.9 1.6

These results show that for synthetic fiber D (PEI10T), and regardless of the hue used, the dyeing kinetics are very fast. Moreover, the red pigment fixes much better than the other elements.

The results obtained on synthetic fibers A and B (PTIT) with respect to reference synthetic fiber C (PTT) show a slightly higher dye affinity, especially with the red and yellow pigments.

The dyeing behavior of synthetic fibers E (PITg) and F (PET) was compared on fabrics knitted from said fibers. The results are presented in FIG. 4 and show that the knitted fabrics obtained with polymer synthetic fibers E have a better dye affinity than those obtained with isosorbide-free synthetic fibers F. Indeed, when comparing the dyes, those obtained on fabrics knitted with synthetic fibers E according to the invention are darker.

The knitted fabrics obtained with synthetic fibers E have a better dye affinity than those obtained with isosorbide-free synthetic fibers F.

Moreover, according to the test of wash fastness of the dyes, no bleeding was observed on the control strips, neither for the textile in synthetic fiber E or for the textile in synthetic fiber F.

This result shows that the synthetic fibers according to the invention thus have a wash fastness similar to that of the synthetic fibers commonly used and that the implementation of a thermoplastic polyester based on isosorbide does not alter this fastness. 

1. A process for manufacturing a colored synthetic fiber comprising the following steps of: 1) providing a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), and at least one aromatic dicarboxylic acid unit (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g; 2) preparing the synthetic fiber from said semicrystalline thermoplastic polyester; and 3) dyeing said synthetic fiber with an aqueous solution of at least one disperse dye.
 2. The process according to claim 1, wherein the disperse dye is selected from azo-type dyes, anthraquinone-type disperse dyes, methine-type dyes, nitro-type dyes, naphthoquinone-type dyes, aminoketone-type dyes and mixtures thereof.
 3. The process according to claim 2, wherein the disperse dye is an azo dye selected from the di-azo dyes or the mono-azo dyes derived from azobenzene.
 4. The process according to claim 1, wherein the aqueous solution of disperse dye used for the dyeing step has a temperature of 120° C. to 140° C., preferably 130° C., and a pH of 3.5 to 5.5, preferably of 4 to
 5. 5. The process according to claim 1, wherein the 1,4:3,6-dianhydrohexitol unit (A) is selected from isosorbide, isomannide, isoidide, or one of the mixtures thereof, preferably, the unit (A) is isosorbide.
 6. The process according to claim 1, wherein the aliphatic diol unit (B) is 1,4-cyclohexanedimethanol.
 7. The process according to claim 1, wherein the aromatic dicarboxylic acid unit (C) is terephthalic acid.
 8. The process according to claim 1, wherein the semicrystalline thermoplastic polyester is free of non-cyclic aliphatic diol unit or comprises a molar amount of non-cyclic aliphatic diol units, with respect to the total number of monomer units of the polyester, of less than 1%; preferably, the polyester is free of non-cyclic aliphatic diol unit.
 9. The process according to claim 1, wherein the preparation step of the synthetic fiber is carried out by the melt spinning method or by wet or dry solution processes.
 10. A synthetic fiber colored by a disperse dye, said synthetic fiber consisting substantially of a semicrystalline thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one aliphatic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), at least one aromatic dicarboxylic acid (C), wherein the (A)/[(A)+(B)] molar ratio is at least 0.05 and at most 0.30, the reduced viscosity in solution (35° C.; ortho-chlorophenol; 5 g/l of polyester) of which is greater than 50 ml/g.
 11. Use of the synthetic fiber as defined according to claim 10, in the field of furnishings, textiles or sporting goods. 